Tractor Cab Virtual Modeling and Ergonomic Evaluation Based on JACK

Aimed at the drawbacks of traditional method of spot evaluation for tractor cabs, such as low effectiveness and high expense, this paper established a new method of tractor cab design and evaluation, which included formulating ergonomic evaluation process, creating virtual models of tractor cab and operators, building virtual environment of tractor cab man-machine system and conducting ergonomic evaluation. The YTO-1604 wheeled tractor has been taken as the analysis object, the layouts of its seat, accelerator pedal, clutch pedal, brake pedal, gear shift lever, steering wheel and other major parts were optimized. The optimized model was created by UG, then it was imported into JACK, thus the object for analysis was created. To accommodate the Chinese tractor operator population, the 95th, 50th and 5th percentile virtual operator models which respectively stands for the big figure, medium figure and small figure of Chinese adult males for ergonomic evaluation were created in JACK, and the angular comfort range for human body joints were determined. The 50th percentile operator was adjusted to a cozy posture through human control module, with hands holding steering wheel, left foot naturally put on clutch pedal, while right foot flat placed on the floor. The operator was located to the h point of seat in the optimized cab model, thus the man-machine virtual environment was completely built. Then the reach zone of the 5th percentile operator and the visual field of the 95th percentile operator were generated, the 95th percentile operator’s comfort was evaluated and the forces of the 95th percentile operator’s spinal L4/L5 were calculated. The results showed that the gear shift lever, steering wheel and control panel were located in the accessible reach zones, conforming to manipulation requirements. Control panel and windshield (except for part of the side windshield which could be observed by moving head) were contained in the visual field, according with vision design standard. The overall comfort score of the 95th percentile operator’s different body parts was 24.5, which indicated that the operator was in good condition and the design conformed to physiological requirements. The lower back compression force of the 95th percentile operator was 742, representing a nominal risk of lower back injury for operators. Thus, the rationality of cab layout scheme was well verified. This paper provides a method for the ergonomic design and evaluation of tractor cabs.